Provision of a secured replica pseudo random noise signal

ABSTRACT

A secure method and a secure provision unit provide a secured replica pseudo random noise signal for a receiver unit. A replica pseudo random noise code is modulated with a noise signal by a receiver-end provision unit. The replica pseudo random noise code has artificially produced noise superimposed thereon, so that the replica pseudo random noise code cannot be read from the noisy signal even at the receiver end, for example within a receiver or on a transmission path between provision unit and receiver.

This application claims the benefit of DE 102014212467.0, filed on Jun.27, 2014, which is hereby incorporated by reference in its entirety.

FIELD

The disclosed embodiments relate to a method and a provision unit forproviding a secured replica pseudo random noise signal for a receiverunit.

BACKGROUND

Pseudo random code sequences, also known as pseudo random noise codes(PRNC) or pseudo random number (PRN) codes, are used for radiotransmission, for example. The codes are spread codes that promptfrequency spreading for an information signal. The wideband transmissionmeans that such a signal has a high level of robustness towardinterference. By way of example, spread sequences are used in satellitenavigation systems such as GPS, Glonass, Beidou or Galileo. In thiscase, the received satellite signal is situated below a noise level. Areceiver is capable of detecting and decoding the emitted signal onlyvia correlation with an appropriate PRN code that the receiver itselfhas available. This is normally the identical PRN code that may alreadybe available in the receiver, for example. It is also possible to referto a replica PRN code, which is a reconstructed or simulated PRN code ora PRN code available as a second version.

Cryptographic PRN codes have been used. In this case, the code sequenceis produced on the basis of a cryptographic key. A receiver is capableof generating the appropriate PRN code for decoding the received signalonly if the receiver knows the PRN code used by the transmitter fortransmitting the signal. For this, the receiver needs the cryptographickey.

The receiver, above all the signal processing on the receiver, needs tobe protected against attackers by security mechanisms in complex fashionin this case. By way of example, an field programmable gate array (FPGA)on which the cryptographic signals are handled needs to be secured byemission protection or tamper-proofing in complex and hence expensivefashion.

Raw data has been digitized and recorded from a received GPS signal. Theraw data is transmitted to a cloud service, so that the signalprocessing is performed on a server. The server is protected in aspecial way in this case, so that the security-critical cryptographicsignal processing takes place in a secure computer center. However, thisrequires a large proportion of the server environment, including datatransmission paths used, to be protected, again in complex fashion.

SUMMARY AND DESCRIPTION

The scope of the present invention is defined solely by the appendedclaims and is not affected to any degree by the statements within thissummary.

The present embodiments may obviate one or more of the drawbacks orlimitations in the related art. For example, the disclosed embodimentsmay provide a secure method and a secure provision unit for providing asecured replica pseudo random noise signal for a receiver unit.

A method provides a secured replica pseudo random noise signal for areceiver unit, in which a replica pseudo random noise code is modulatedwith a noise signal by a receiver-end provision unit. In this case, thereplica pseudo random noise code is protected by the noise signal thatis modulated on or added. This prevents or at least significantlycomplicates the possibility of the replica pseudo random noise codecontained in the secured signal being extracted therefrom.

A replica pseudo random noise code means a code sequence that is used ina correlation method at the receiver end in order to be able to detector decode a received signal from a transmitter, the transmitter havingused a pseudo random noise code associated with the replica pseudorandom noise code for the purpose of modulating the signal. A replicapseudo random noise code together with a pseudo random noise codetherefore forms a pair that needs to match, e.g., be identical, inrespect of the bit sequence of the code so that the pseudo random noisecode of the received signal is detectable or decodable at the receiverend. In the case of a cryptographically produced pseudo random noisecode used by the transmitter, the appropriate, e.g., identical,symmetrical key is also present at the receiver end so that theappropriate replica pseudo random noise code is produced.

At the receiver end, the replica pseudo random noise code is modulatedwith a noise signal. That is to say that the replica pseudo random noisecode has artificially produced noise superimposed on it, so that thereplica pseudo random noise code cannot be read from the noisy signaleven at the receiver end, for example within a receiver or on atransmission path between provision unit and receiver. Hence, thereplica pseudo random noise signal is protected against the replicapseudo random noise code being read. The replica pseudo random noisesignal is therefore secured as soon as the signal leaves thereceiver-end provision unit. Manipulation protection or emissionprotection needs to be ensured at the receiver end only for a verylimited area. Only the provision unit is provided with specialprotection, for example via tamper-proofing measures. The replica pseudorandom noise code in need of protection is therefore provided for thereceiver unit only in a form in which the code cannot feasibly be put tomisuse. For instance, the code cannot be used, or can be used only to arestricted degree, to transmit an interference signal itself. Should thereplica pseudo random noise code be available on the receiver inunsecured form, the code can be used in order to modulate aninterference signal. A manipulated receiver is capable of thereforefeigning being in possession of the original pseudo random noise codeand hence being the legitimate sender of an actually manipulated signal,for example, a satellite signal.

The production of cryptographic pseudo random noise codes—and hence alsoof cryptographic replica pseudo random noise codes—involves acryptographic key. The cryptographic algorithms associated therewith maybe time-consuming and resource-using. The secured replica pseudo randomnoise signal may be deposited, e.g., stored, at the receiver end over arelatively long period, because misuse is not readily possible even whenthe secured replica pseudo random noise signal is read from a memoryarea. Hence, a receiver unit or a receiver may already receive and storethe secured replica pseudo random noise signal even before signalprocessing that is to be performed, for example before a received signalis received. For the processing of a realtime-critical signal, thesignal processing time may be reduced, because the secured replicapseudo random noise signal is already available.

According to one refinement, a modulated replica pseudo random noisesignal is generated from the replica pseudo random noise code. Thereplica pseudo random noise code, which is a bit sequence, may berepresented as a digitized signal. A modulation method thereforeinvolves the receiver end first of all producing a modulated replicapseudo random noise signal from the replica pseudo random noise codebefore the further modulation steps are performed.

According to one refinement, the noise signal has a higher level thanthe modulated replica pseudo random noise signal. The replica pseudorandom noise code is intended to be hidden in the additionally added,artificial noise. This warrants a level of the noise signal high enoughfor the characteristic code not to be able to be read. The noise signalis modulated onto the modulated replica pseudo random noise signal,which may be the digitized signal from the replica pseudo random noisecode. A correlator provided with the replica pseudo random noise signalfor decoding correlates the received signal with the replica pseudorandom noise signal. The noise level is accordingly matched to the levelof the modulated replica pseudo random noise signal.

According to one refinement, the secured replica pseudo random noisesignal is correlated with a received signal received by the receiverunit. In this case, a received signal that may be received by thereceiver unit is correlated, e.g., continuously, in a signal processingstage. Hence, sections in which a signal, for example a datatransmission signal or a satellite signal, is recognized by virtue ofthe correlation, and sections in which a result of the correlation isthat the receiver does not recognize a signal emitted by a transmitter,can alternate.

According to one refinement, a pseudo random noise code contained in areceived signal received by the receiver unit may be decoded via acorrelation method using the secured replica pseudo random noise signal.Hence, the signals from a transmitter that have been modulated with thepseudo random noise code may be recognized by the receiver unit. Onlyfor matched pseudo random noise codes and replica pseudo random noisecodes does the correlation method allow decoding of the received signal.The noise signal superimposed on the replica pseudo random noise code isnot detrimental to the performance of the correlation in this case. Thenoise signal is used for the correlation and acts as an intentionalsource of interference. In a corresponding coding method that is robustwhen subject to interference to a certain degree, the decoding is stillpossible.

According to one refinement, a pseudo random noise signal contained in areceived signal received by the receiver unit is evaluated via acorrelation method. In this case, a time offset between the receivedsignal with the pseudo random noise signal and the replica pseudo randomnoise signal produced for the receiver end may be ascertained. Timeinformation or position information or distance information may also bedetermined, e.g., provided that a plurality of satellite signals arereceived by the receiver unit.

According to one refinement, the replica pseudo random noise code isgenerated by a replica pseudo random noise code generator of theprovision unit or by an external replica pseudo random noise codegenerator that may be connected to the provision unit.

Because the replica pseudo random noise code is unsecured as such,transmission by an external unit warrants ensuring the integrity andnon-monitorability of the transmission path. The replica pseudo randomnoise code generator is protected against reading or unauthorizedaccess, e.g., via protective measures.

According to one refinement, the replica pseudo random noise codegenerated is a cryptographic replica pseudo random noise code. In thiscase, the secure production of the cryptographic replica pseudo randomnoise code is dependent on the availability and secrecy of acryptographic key. The evaluation of a received signal with a pseudorandom noise component via correlation with the replica pseudo randomnoise signal may therefore confirm information about the integrity ofthe received signal transmitted by the transmitter if the result of thecorrelation is a match between cryptographic pseudo random noise codeand cryptographic replica pseudo random noise code. Hence, transmitterand receiver have the same cryptographic key.

According to one refinement, the noise signal is in the form of a randomor pseudo random noise signal. In this case, the noise signal isintended to emulate natural, nondeterministic noise and needs to meetthe requirements that firstly the replica pseudo random noise code isnot meant to be recognizable in the modulated replica pseudo randomnoise signal and secondly the interference by the noise signal is not sogreat that the correlation with the received signal does not allow apseudo random noise signal that is contained to be recognized.

According to one refinement, the replica pseudo random noise code ismodulated by the provision unit by adding it to the noise signal. Thisis a low-complexity, e.g., resource-saving, modulation variant. However,other modulation methods are also suitable for forming a protectedreplica pseudo random noise signal from a replica pseudo random noisecode and a noise signal. In principle, any modulators, e.g., a push-pullmixer, ring mixer or ring modulator, a transformer, or signalcombination operations such as addition, subtraction, multiplication,table lookups, etc., may be used. These methods may be performedelectronically, but also digitally in the form of digital signalprocessing by a digital signal processor (DSP), or by a digital signalprocessing arrangement on a programmable logic chip or FPGA or anapplication specific integrated circuit (ASIC) or a signal processingintegrated circuit.

According to one refinement, the noise signal is generated by a noisegenerator of the provision unit or by an external noise generator thatmay be connected to the provision unit. The noise signal does not needto be specially protected against spying and may be provided by aseparate unit that is suitable for this purpose.

According to one refinement, a level of the noise signal is generated soas to be constant over time or so as to be variable over time. Thesignal strength that may be expected for the received signal at theexpected location of the receiver may be taken into account. Thespecific restriction that the receiver only detects a received signal ifthe signal strength thereof exceeds a threshold value may be set. If thereceiver is at too great a distance from the expected location, itcannot detect the pseudo random noise signal despite the correlationmethod and presence of the appropriate replica pseudo random noise code.The specific effect that a receiver has only restricted robustnesstoward sources of interference, which are known as interferers, may alsobe achieved.

According to one refinement, the secured replica pseudo random noisesignal is provided for the receiver unit by a security module or asecurity cloud server, e.g., continuously or in the form of individualsections or with the addition of supplementary information. The receivermay therefore be realized in distributed fashion and the provision unitmay be in the form of an external unit, e.g., in the form of a securitymodule or security cloud server, separately from a receiver unit.Because the secured replica pseudo random noise signal is protectedagainst being read, it may be sufficient for the security module or thesecurity cloud server to be protected against attackers by appropriatesecurity measures. Hence, the area of a receiver to be protected byprotective mechanisms may be substantially reduced in size. Thisprotected, secured area may be realized on a server and the protectedreplica pseudo random noise signal may be provided via a networkconnection. The latter may additionally be protected by securitymechanisms, such as a cryptographically secured communication link.

According to one refinement, the secured replica pseudo random noisesignal has a marker for identifying a signal produced at the receiverend. Hence, a receiver of a received signal may, following decoding,recognize a supposed pseudo random noise signal, but then see, inaddition to the supposed pseudo random noise signal, for instance, anInvalid marker or an Invalid marker signal or an Invalid marker codethat reveals that said signal is a replica pseudo random noise signalwith a marker, generated at the receiver end. This allows a receiver todistinguish whether a signal is an original signal, for example asatellite signal, or a signal emitted by a receiver end, e.g., amanipulated receiver. An Invalid marker signal may be contained in thereplica pseudo random noise signal as a further pseudo random noise codebeneath the noise signal. Despite knowledge of the Invalid marker pseudorandom noise code, it is therefore barely possible to remove the Invalidmarker signal from the replica pseudo random noise signal withoutdestroying or altering the replica pseudo random noise code contained,e.g., the actual useful code that the receiver uses for the correlationand the coding, in the process.

A provision unit provides a secured replica pseudo random noise signalfor a receiver unit having a modulator for modulating a replica pseudorandom noise code with a noise signal. In this case, the modulator isdesigned to modulate signals, for example via addition.

According to one refinement, the provision unit additionally has areplica pseudo random noise code generator for providing the replicapseudo random noise code. According to one refinement, an externalreplica pseudo random noise code generator that may be connected to theprovision unit is provided. The replica pseudo random noise codegenerator is protected against an attack, such as spying or reading, toa particular degree, because the replica pseudo random noise code isavailable in unsecured form.

According to one refinement, the noise signal is generated by a noisegenerator of the provision unit or by an external noise generator thatmay be connected to the provision unit. The noise generator may not bespecially protected, beyond usual protective measures, against attacksbecause it is not possible to reconstruct any information about thesecured replica pseudo random noise code from the noise signal.

According to one refinement, a key generator or key memory is designedto produce a cryptographic key, in which the cryptographic key may beused to generate a cryptographic replica pseudo random noise code.

According to one refinement, the provision unit is produced on areceiver having a receiver unit. In this case, the provision unit may beadjusted to be equipped with special protective mechanisms, such asparticularly tamper-proofing apparatuses.

According to one refinement, tamper-proofing for recognizingmanipulation or damage is provided for the provision unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic illustration of a method for providing asecured replica pseudo random noise signal in accordance with oneembodiment.

FIG. 2 shows a schematic illustration of a receiver with a receiver unitand a provision unit in accordance with one embodiment.

FIG. 3 shows a schematic illustration of a receiver with a receiver unitand a provision unit in accordance with another embodiment.

DETAILED DESCRIPTION

FIG. 1 schematically shows how, in a first step, modulation A of areplica pseudo random noise code 10 with a noise signal 12 by areceiver-end provision unit 3 is provided. The modulation generates asecured replica pseudo random noise signal 13 and, in a second step,provision B, provides it for a receiver unit 2. In this case, themodulation A is effected at a time before the provision B. Hence, onlyone secured replica pseudo random noise signal 13 is intended to beprovided, e.g., outside a protected environment on a receiver.

FIG. 2 schematically shows how a receiver 1 with an integrated provisionunit 3 according to a first exemplary embodiment is designed. Thereceiver 1 has an antenna socked AC that may be used to connect anantenna ANT. A received signal 130 provided by the antenna ANT is firstof all handled by a radiofrequency assembly, or radiofrequency front end(RFFE). In this case, filtering and amplification take place. The signalis then provided for a down converter DC that mixes the signal with asignal from a local oscillator LO and hence performs down conversion.The signal is then provided for an analog/digital converter AD. Thelatter forwards the digitized signal to the baseband processing BB. Inthis case, the receiver is controlled by a controller or control unitCU. The latter configures the individual assemblies, for example inorder to select an appropriate frequency band by changing the frequencyof the local oscillator LO or, by way of example, in order to configurethe input filter of the radiofrequency assembly RFFE or, by way ofexample, in order to configure the bandwidth or sampling rate of theanalog/digital converter or in order to select a modulation method forthe baseband processing. The baseband processing BB may be realized on afield programmable gate array (FPGA) chip. The baseband processing BB isprovided with a secured replica pseudo random noise signal 13 by aprovision unit 3. For this, the provision unit 3 has a replica pseudorandom noise code generator 4. A key generator 6 or key memory 6′ isadditionally provided for the purpose of producing or storing acryptographic key K. The replica pseudo random noise code generator 4 isdesigned to generate a cryptographic replica pseudo random noise code10K and selects a suitable cryptographic key K, e.g., according to thefield of use or according to the location at which the receiver 1 issituated or according to the time at which signal processing is intendedto take place. A plurality of keys may be provided, from which arespective specific replica pseudo random code is generated. By way ofexample, different keys are provided for different satellite systems. Inaddition, a noise generator 5 that produces a noise signal 12 isprovided on the provision unit 3. The noise signal 12 and thecryptographic replica pseudo random noise code 10K are supplied to amodulator 7. The latter internally performs modulation of thecryptographic replica pseudo random noise code with the noise signal, inwhich a replica pseudo random noise signal 11, e.g., a digitized signal,is produced in an intermediate stage. The noise signal 12 has a highersignal level than the replica pseudo random noise signal 11. Themodulator 7 may be used by the provision unit 3 to provide the replicapseudo random noise code 13 that is secured via the modulation with thenoise signal 12. The provision B is effected at a receiver unit 2 of thereceiver 1. This may be the baseband processing BB, for example, theFPGA, and also a PVT component PVT, which is a software implementationon a central processing unit (CPU), for example. The PVT component PVTis the evaluation unit of the receiver unit 2 and ascertains position,speed and time, for instance, from a satellite signal. The component ofthe baseband processing BB has a correlator C provided on it thatcorrelates the secured replica pseudo random noise signal 13 with thedigitized received signal. The secured replica pseudo random noisesignal 13 is in a form in which it is not possible to tell whether thesignal contains the underlying cryptographic replica pseudo random noisecode 10K. The received signal 130 or the digitized received signal alsocannot be regarded as having the presence of a pseudo random noise codeon account of the superimposition with natural noise. The securedreplica pseudo random noise signal 13 thus cannot be used to emit afaked signal with a valid pseudo random noise code.

Special protection against attackers may be provided for the provisionunit 3 or at least for the modulator 7 with replica pseudo random noisecode generator 4. This ensures that the replica pseudo random noise codebecomes known to an attacker in a phase in which it is not yet hidden inthe noise signal 12 as a result of this noise signal being modulated on.The provision unit 3 may be in the form of a tamper-proofcryptocontroller.

In comparison with conventional security measures, it is now no longernecessary to have physical protection for the entire receiver or thecritical assemblies such as the baseband processing, the PVT componentor the control unit. By way of example, tamper-proofing may be achievedby casting in epoxy resin or the introduction of an anti-drilling foil,what is known as a wire mesh. Advantageously, such a tamper-proofingapparatus may, according to this first exemplary embodiment, be reducedto a minimum within the provision unit 3. Lines or communication linksthat have hitherto transmitted critical signals are also now protectedonly within the provision unit 3. This allows a secure low-cost receiverto be realized.

FIG. 3 shows a second exemplary embodiment, in which the receiver isrealized in distributed fashion. Elements having the same function areprovided with the identical reference symbols in FIGS. 2 and 3, unlessotherwise stated.

According to the second exemplary embodiment, the receiver 1 has a firstnetwork interface IF1 to a network NW. The receiver 1 may use thenetwork NW to communicate with a cloud offload server COS. The cloudoffload server COS performs a portion of the signal processing. Thecloud offload server COS has a second network interface IF2 to thenetwork NW. In addition, the cloud offload server COS holds theprovision unit 3 for the purpose of provision B of the secured replicapseudo random noise signal. A memory area M′ is used to store thesecured replica pseudo random noise signal 13 as a snippet, e.g., as alimited signal section. This may be a digitized signal segment that isprovided for the network via the second network interface IF2 of thecloud offload server COS and hence for the receiver unit 2 of thereceiver 1 via the first network interface IF1. In this example, thereceiver unit 2 denotes the control unit CU, the baseband processing BB,the PVT component PVT, the radiofrequency assembly RFFE, the downconverter DC, the analog/digital converter AD, the local oscillator LOand additionally a code memory M. By way of example, the protectedreplica pseudo random noise signal 13 is transmitted to the control unitCU of the receiver unit 2, which stores the replica pseudo random noisesignal 13 in the code memory M provided for this purpose. From this codememory M, the correlator C may read the secured pseudo random noisesignal 13 for the purpose of performing the correlation and may decode areceived signal 130 that has the matching pseudo random noise code 100.The result of the correlation is forwarded to the PVT component PVT forthe purpose of ascertaining a time offset.

The cryptographic replica pseudo random noise code 10K is generatedoutside a receiver 1 installed in the field, e.g., in order tofacilitate key management. The cloud offload server COS may ask anappropriate key manager about currently valid keys and transmitters ofexpected received signals via secured communication links and in anenvironment protected against attackers. The critical transmission, tobe protected against attacks, from a cloud server that provides areplica pseudo random noise code to a receiver is complex or, dependingon the field of use, non-implementable. The use of the provision unit 3according to the second exemplary embodiment allows more favorabletransmission in the event of the computation of the cryptographicreplica PRN code 10K or of a cryptographic replica PRN code sectionbeing effected on an external server. Hiding the cryptographic replicaPRN code 10 in an artificially produced noise signal within theprovision unit 3 and, for example, within the server COS prior to thetransmission of a signal to the receiver 1 externally may allow theunsecured transmission of the cryptographic replica pseudo random noisecode 10K to the receiver 1 via the network NW.

The entire server COS or alternatively just the provision unit 3 may berealized in protected form. The network NW may be a communicationnetwork, such as TETRA, UMTS, LTE, WLAN or WiMAX. The network NW mayalso be the Internet or a self-contained IP-based network.

An attacker manipulating the receiver 1 nevertheless cannot start ameaningful attack with a secured replica pseudo random noise signal 13that may be read from the receiver 1, because the attacker cannotreconstruct a pseudo random noise code 10K from the signal. Hence, thereceiver 1 cannot transmit a manipulated signal with a correct pseudorandom noise signal, e.g., as a result of an attacker. An attack on thenetwork connections within the network NW also continues to beunsuccessful, because the original cryptographic replica pseudo randomnoise code 10K is available only in secured form hidden in the noisesignal 12.

It is to be understood that the elements and features recited in theappended claims may be combined in different ways to produce new claimsthat likewise fall within the scope of the present invention. Thus,whereas the dependent claims appended below depend from only a singleindependent or dependent claim, it is to be understood that thesedependent claims may, alternatively, be made to depend in thealternative from any preceding or following claim, whether independentor dependent, and that such new combinations are to be understood asforming a part of the present specification.

While the present invention has been described above by reference tovarious embodiments, it should be understood that many changes andmodifications may be made to the described embodiments. It is thereforeintended that the foregoing description be regarded as illustrativerather than limiting, and that it be understood that all equivalentsand/or combinations of embodiments are intended to be included in thisdescription.

1. A method for providing a secured replica pseudo random noise signalfor a receiver unit, the method comprising: modulating a replica pseudorandom noise code with a noise signal by a receiver-end provision unit.2. The method of claim 1, further comprising generating a modulatedreplica pseudo random noise signal from the replica pseudo random noisecode.
 3. The method of claim 2, wherein the noise signal has a higherlevel than the modulated replica pseudo random noise signal.
 4. Themethod of claim 1, further comprising correlating the secured replicapseudo random noise signal with a received signal received by thereceiver unit.
 5. The method of claim 1, further comprising decoding apseudo random noise code contained in a received signal received by thereceiver unit via a correlation method using the secured replica pseudorandom noise signal.
 6. The method of claim 1, further comprisingevaluating a pseudo random noise signal contained in a received signalreceived by the receiver unit via a correlation method.
 7. The method ofclaim 1, further comprising generating the replica pseudo random noisecode by a replica pseudo random noise code generator of the provisionunit or by an external replica pseudo random noise code generatorconnected to the provision unit.
 8. The method of claim 1, wherein thereplica pseudo random noise code is a cryptographic replica pseudorandom noise code.
 9. The method of claim 1, wherein the noise signal isconfigured as a random noise signal or as a pseudo random noise signal.10. The method of claim 1, further comprising modulating the replicapseudo random noise code by the provision unit by adding the replicapseudo random noise code to the noise signal.
 11. The method of claim 1,further comprising generating the noise signal by a noise generator ofthe provision unit or by an external noise generator connected to theprovision unit.
 12. The method of claim 1, further comprising generatinga level of the noise signal so as to be constant over time or so as tobe variable over time.
 13. The method of claim 1, further comprisingproviding the secured replica pseudo random noise signal for thereceiver unit by a security module or by a security cloud server, eithercontinuously or in individual sections or with addition of supplementaryinformation.
 14. The method of claim 1, wherein the secured replicapseudo random noise signal comprises a marker for identifying a signalproduced at the receiver end.
 15. A provision unit for providing asecured replica pseudo random noise signal for a receiver unit, theprovision unit comprising: a modulator configured to modulate a replicapseudo random noise code with a noise signal.
 16. The provision unit ofclaim 15, wherein a pseudo random noise code contained in a receivedsignal received by the receiver unit is decodable via a correlationmethod using the secured replica pseudo random noise signal.
 17. Theprovision unit of claim 15, further comprising a replica pseudo randomnoise code generator configured to generate the replica pseudo randomnoise code.
 18. The provision unit of claim 15, further comprising anoise generator configured to generate the noise signal.
 19. Theprovision unit of claim 15, wherein a key generator or a key memory isconfigured to produce a cryptographic key, wherein the cryptographic keyis configured to generate a cryptographic replica pseudo random noisecode.
 20. The provision unit of claim 15, wherein the provision unit isproduced on a receiver having a receiver unit.
 21. The provision unit ofclaim 20, wherein tamper-proofing to recognize manipulation or damage isprovided for the provision unit.